Hops gives beer its unique aroma and bitterness, and also helps to sediment out excess protein and suppress bacterial proliferation. However, as the extent to which hops act in this way varies mainly according to the variety, it is necessary to identify hop varieties in order to manufacture beer of consistent quality and develop new beers.
Conventionally, the identification of hop varieties was based on their constituent components, e.g. bitter components (.alpha. acid/.beta. acid cohumulone/humulone, colupulone/lupulone) and essential oil components (farnesene, caryophyllene).
However, in addition to the fact that this identifying method based on bitterness and oils requires a great amount of effort for measuring all the components, it was also unable to determine the varieties precisely because, even for the same variety, these components vary widely depending on the harvesting location and year. Due to recent progress in genetic engineering, various attempts have been made to elucidate sequences of chromosomes depending on the plant species, and based on the base sequences found, to identify strains from differences in genetic information between different plants or varieties of the same plant, i.e. from the polymorphism of DNA sequences.
An identification of plant variety based on this kind of polymorphism is reliable because the DNA sequence itself is not easily affected by environmental influences, and is therefore invariant.
In this regard, the present invention provides a reliable and simple method of identifying hop varieties using the aforesaid genetic technique.